1. Field of the Invention
The present invention relates to an image pickup apparatus such as a digital camera, etc.
2. Description of the Related Art
There is a shutter device used in an image pickup apparatus such as a digital camera, etc., as described in Japanese Utility Model Publication No. Hei 6-26895 (hereinafter referred to as Patent Document 1). The shutter device described in Patent Document 1 includes both a front curtain and a rear curtain. Explanation is here focused on the operation of the rear curtain.
In such a shutter device, a drive lever for driving a rear curtain (a rear curtain drive member) is pivotably shifted to a given position by a cam member (a charge member) at the time of shooting to charge a drive-purpose spring of the drive lever.
The drive lever is held by an electromagnet at the point of time when the rear curtain is shifted to the exposure start position. Specifically, after the rear curtain has been shifted to the exposure start position along with the pivoting movement of the drive lever, the energization of the electromagnet is started. Incidentally, the electromagnet is disposed at a position opposed to the iron piece of the drive lever when the rear curtain is at the exposure start position. Further, in response to the start of the energization, the iron piece is attracted by the electromagnet so that the biasing force of the charge spring is cancelled by the attractive force of the charge spring. Such attractive action of the electromagnet maintains the drive lever at a given position as well as the rear curtain at the exposure start position. A cam member which has shifted the drive lever to the given position is shifted to an appropriate retreat position so as not to hinder the traveling movement of the rear curtain, which is described later.
Thereafter, the front curtain travels and then the energization of the electromagnet is ceased so that the rear curtain travels. Specifically, in response to such de-energization, force (electromagnetic attractive force) counteracting the biasing force of the charge spring disappears. Therefore, the biasing force allows the drive lever to start to shift. Along with the shifting operation, the rear curtain shifts from the exposure start position toward the exposure end position.
Japanese Patent Laid-Open No. 2003-15190 (hereinafter referred to as Patent Document 2) describes the technology in which a drive lever having shifted a rear curtain to an exposure start position is held using not the magnetic force of an electromagnet but the pressing force of a mechanical holding mechanism. Specifically, the charge member (setting member) for charging a spring force regarding the drive member comes into contact with the drive lever to apply a pressing force thereto. In this way, the drive lever is held. Thereafter, when the rear curtain is driven, operation for releasing the holding of the drive lever (specifically, the turning operation of the charge member) is executed before the driving operation of the rear curtain.